1. Field of the Invention
The present invention relates to a heat processing apparatus to conduct heat processing on a heat processed sheet, and particularly to the preliminary heating in the heat developing apparatus using a dry material for which the wet processing is not necessary.
2. Description of the Related Art
For example, in a plate making image recording apparatus photoengraving for printing, or a digital radiography system using a heat accumulating fluorescent substance sheet, image recording apparatus for recording a medical image such as CT, or MR (Magnetic Resonance), a wet system in which, after photographing or recording in silver halide photographing photosensitive material, an image is obtained by wet processing, is used.
In contrast to that, recently, a recording apparatus by a dry system in which the wet processing is not necessary, is remarked. In such the recording apparatus, a photosensitive and/or heat sensitive recording material (photosensitive heat sensitive recording material) or film of heat developing photosensitive material (hereinafter, called recording material) is used. Further, in the recording apparatus by this dry system, in an exposure section, laser beams are irradiated (scanning) on the recording material and a latent image is formed, and in the heat developing section, the recording material is brought into contact with a heating means for heat developing, and the recording material on which the image is formed, is delivered to the outside of the apparatus.
Such the dry system, not only the image can be formed in a shorter time as compared to the wet processing, but a problem of waste solution processing in the wet processing can also be solved, thereby, it is fully presumed that its demand is increased after now.
In this connection, in a preliminary heating in the heat developing apparatus, when the heat developing sheet whose dimension in the width direction is narrow, or the heat developing sheet whose thickness is large and stiffness is high, is heated from the room temperature to the developing temperature, a wrinkle is hardly generated even by the heating, accordingly, the counter measure for the wrinkle is not necessary, however, when the heat developing sheet whose dimension in the width direction is wide, or the heat developing sheet whose thickness is small (hereinafter, called xe2x80x9csheetxe2x80x9d), is heated from the room temperature to the developing temperature, the processing quality deterioration due to the wrinkle by the expansion and contraction of the sheet by the heating is generated. In order to control the processing quality deterioration, conventionally, the following countermeasures are taken.
1) One of them is that, when the temperature of each of the rotating bodies is individually set so that a plurality of rotating body pairs are nipping the sheet and it can be heated and conveyed in stages, the generation of wrinkles in the sheet can be suppressed. Because the plurality of rotating bodies nip the sheet, principally, the buckling deformation due to the heat expansion and contraction of the sheet occurs, and sometimes wrinkles are generated. These wrinkles deteriorate the processing quality. Accordingly, in order to increase the quality, further addition of plural stages of heat rotating body pairs is necessary, which results in the increase of the number of mechanical parts and the increase of the apparatus size.
2) Another one is that, when the rotating bodies are arranged in zigzag, the sheet is not nipped by the rotating bodies, and heated and conveyed, thereby, the buckling deformation is hardly generated, and the sheet is heated and conveyed. However, there is sometimes a case in which, due to the initially existing curl of the sheet itself and the difference of the values of physical properties (friction coefficient, coking property) of the front and rear surfaces of the sheet, from the viewpoint of the conveyance property, the reliability is lowered.
Nowadays, a completely dry heat developing apparatus for the common commercial printing is developed on the base of the heat developing apparatus developed for the news paper company in initial times, however, a largely different point from the news paper field is that, in the common commercial printing field, the size of the latent image formed in the heat developing sheet becomes fine, and becomes sensitive to the dispersion of the development temperature and the development time, and that is, a point in which the processing quality deterioration due to the wrinkle is emphasized. Further, the more increase of the processing quality is required. Further, in the common commercial printing field, the WET processor is already supplied to the market at low cost, and it is required to avoid the cost-up due to the increase of the number of mechanical parts to increase the processing quality or the increase of the size of the apparatus, and on the contrary, inversely, the large reduction of the cost from the present cost is required.
Accordingly, the problem to be solved by the present invention is to provide a heat developing apparatus provided with an effective heat conveying section by which, without lowering the sheet conveying performance, while the processing quality is increased, the cost can be reduced. Further, another problem to be solved by the present invention is, as described above, while the processing quality is being increased, to improve the processing quality deterioration of a sheet leading edge portion caused by the difference of the behavior between the sheet leading edge portion and the other portion in the time of the sheet heat conveying.
In order to solve the above described problems, the heat developing apparatus according to the first aspect of the invention is characterized in that, in the heat developing apparatus to heat the heat developing sheet on which a latent image is formed by the exposure, to the developing temperature through a preliminary heating means, the preliminary heating means has a plurality of rotating body pairs to nip the heat developing sheet and to heat convey to the developing temperature, and the rotating body pairs are arranged so that at least one pair of rotating body pair in the plurality of rotating body pairs changes the conveying direction of the heat developing sheet.
The second aspect of the invention is the heat developing apparatus characterized in that, in the heat developing apparatus to heat the heat developing sheet on which a latent image is formed by the exposure, to the developing temperature through a preliminary heating means, the preliminary heating means has a plurality of rotating body pairs to nip the heat developing sheet and to heat convey to the developing temperature, and the rotating body pairs are arranged so that at least one pair of rotating body pair in the plurality of rotating body pairs changes the conveying direction of the heat developing sheet, and further, after the heat developing sheet is brought into contact from the tangential line direction of the point on the outer periphery of one rotating body constituting the rotating body pairs, the heat developing sheet is nipped.
The third aspect of the invention is, in the heat developing apparatus of the first aspect or the second aspect, characterized in that respective changes of the heat developing sheet conveying direction on the plurality of rotating body pairs are the same rotating direction around one rotating body axis center respectively arranged in the same manner in respective rotating body pairs.
The fourth aspect of the invention is, in the heat developing apparatus of any one aspect of the first aspect to the third aspect, characterized in that each of the plurality of rotating body pairs are structured by two rollers, and at least one roller is a heating roller provided with the heating means, and the arrangement, interval and temperature of the heating roller is set so that it has the temperature difference by which the heat developing processing quality deterioration due to the heat deformation of the heat developing sheet is not generated.
The fifth aspect of the invention is, in the heat developing apparatus of the fourth aspect, characterized in that the heating roller has the thick-wall metallic pipe and the heat source section arranged in the axis center of the metallic pipe, and a plurality of members whose heat conductivity is greater than the metallic pipe are buried at equal interval in the peripheral direction of the wall-thickness portion of the metallic pipe.
The sixth aspect of the invention is, in the heat developing apparatus of any one of the first aspects to the fifth aspect, characterized in that the rotating body surface material of the plurality of rotating body pairs in contact with the surface on which the latent image of the heat developing sheet is formed, is formed of silicon, and the heat developing sheet is deformed and conveyed in the same rotating direction around the axis center of the rotating body whose surface is structured by the silicon rubber.
The seventh aspect of the invention is, in the heat developing apparatus of any one of the first aspect to the sixth aspect, characterized in that the rotating body pair nips the heat developing sheet by the self weight load of the rotating body, and the rotating body arranged above the rotating body pair can be moved to the surface direction connecting the axis center of the rotating body pair.
As described above, according to the present invention, because a plurality of rotating body pairs to nip the sheet to heat-convey it up to the developing temperature are arranged in a manner that the sheet can be conveyed while the rotating direction is being changed along the outer periphery of one portion, and also in a manner that the temperature of each rotating body can be individually set so that the sheet temperature can be heated in stages by each rotating body pair, the sheet is conveyed under curved condition, and the cost of this system can be reduced while the conveyance performance is not lowered, and the processing quality is increased.
Further, as described above, while the processing quality is increased, according to the invention of the second aspect, the processing quality deterioration of the sheet leading edge portion caused by the difference of the behavior between the sheet leading edge portion and the other portion at the time of the sheet heat conveying can be improved.